Merozoite stage

An anopheline mosquito inoculates plasmodium sporozoites to initiate human infection (Figure 52-1). Circulating sporozoites rapidly invade liver cells, and exoerythrocytic stage tissue schizonts mature in the liver. Merozoites are subsequently released from the liver and invade erythrocytes. Only erythrocytic parasites cause clinical illness. Repeated cycles of infection can lead to the infection of many erythrocytes and serious disease. Sexual stage gametocytes also develop in erythrocytes before being taken up by mosquitoes, where they develop into infective sporozoites. 

Oral administration of polyether antibiotics allows, initially, for regulation of the body function at the site of digestion by positively affecting feed conversion efficiency and negatively affecting the developmental stage of coccidia. Since their activity is directed particularly towards sporozoites and merozoites, the polyethers must be fed continuously to be fully effective but are not recommended for treating established infections. They have a low therapeutic index and may... 

Interest in vaccine development has centered around the asexual erothrocytic stage of the life cycle, especially the merozoite. Several proteins associated with these stages have been identified and produced by recombinant techniques (92,93). The most prominent is the MSA-1 protein of the merozoite. A clinical trial with this protein is being planned (93). 

Merozoite—The motile, infective stage of malaria, responsible for disease symptoms. 

Malaria is transmitted by the bite of an infected Anopheles mosquito that introduces the sporozoites (tissue parasites) of the plasmodia P. falciparum, P. vivax, P. malariae, and P ovale) into the bloodstream. The asexual reproduction stage develops in humans, whereas the sexual stage occurs in the mosquito. The sporozoites invade parenchymal hepatocytes, multiply in stages referred to as exoery-throcytic stages, and become hepatic vegetative forms or schizonts. Schizonts rupture to release daughter cells, or merozoites, that then infect erythrocytes. 

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